The present disclosure relates to lighting devices and methods. In particular, the present disclosure relates to a method and system for chromaticity adjustment or color matching for a video display screen.
Today, it is common for video displays to use light emitting diodes (“LEDs”) because of the brightness and low power requirements of the LEDs. LED video screens are used as digital billboards to display e.g., advertisements, textual and/or graphical informational messages, and live or prerecorded videos throughout cities and towns and at sporting events, concerts, and other appropriate venues (e.g., inside or outside of buildings). LED video screens, also referred to as LED display walls, are made up of individual panels and/or intelligent modules (IM) having a predetermined number and arrangement of controllable LEDs. The panels and/or modules are mounted next to each other and their outputs are controlled such that they appear to be one large display screen.
The LEDs used in the LED video screen, etc. are usually red, green or blue (“RGB”) LEDs whose output can be controlled such that the RGB components mix according to known principles to create any visible color (including black and white). Unfortunately, the batches of LEDs that are used for the modules, panels, etc. may have different wavelengths of color due to e.g., their composition, manufacturing and/or other differences. This means that the LEDs on the individual panels and modules may have different output coloring from panel to panel and module to module. Since video screens comprise multiple panels and/or modules placed next to each other, uniformity of the screen's output will be affected by the color differences between the LED batches.
Sometimes, when constructing an LED video screen, panels and/or modules are discarded when it is determined that there are color differences between the other panels and/or modules in the screen. That is, only compatible panels and modules are used, so that screen uniformity can be achieved as best as possible. This, however, wastes resources and can be expensive. Moreover, exact color uniformity is not guaranteed.
There have been attempts to adjust the LED video screen's uniformity by adjusting the saturation, luminance and hue of the panels making up the screen. This is often referred to as chromaticity adjustment or color matching. These attempts, however, necessarily alter the RGB output gain, which also affects the output white balance of the panels/modules. Therefore, uniformity based on the saturation, luminance and hue adjustments will not be achieved because the panels/modules will have different RGB gain and white balancing. Likewise, if a target white balance is desired between the panels and modules, then uniformity will not be achieved because of the different RGB ratios. Thus, these techniques are not desirable and will not result in a uniform screen output.
Accordingly, there exists a need to provide an improved color matching/chromaticity adjustment technique for a video screen, display panel, module or other component comprising different batches of light emitting diodes.